Trans acting elements are those elements which are specific
to other than core promoter element(TATA box)eg.GC box,CAAT
box which are located several bp upstream to the core
promoter element.This may act during induction in specific
tissues i.e. during tissue specific expression contol.They
can also be known as Specialized Transcription
Factors.Whereas transcription factors facilitate the binding
of the RNA polII into the core promoter element sequence and
conduit the trancription i.e. generalised transcription factors.